Situational awareness is essential for a safe and sustainable urban environment. While the wide deployment of Internet of Video Things (IoVT) enables efficient monitoring of the footage of the Smart Cities, it also attracts attackers and abusers. Disinformation injected into the IoVT can mislead the city administrations, policy makers, and emergency responders, and lead to disastrous consequences. It is very challenging to timely authenticate each video stream from pervasively deployed IoVT devices. This article presents a Blockchain Enhanced Video input Authentication (BEVA) scheme as an edge service to fight against the visual layer attacks on smart IoVT systems such as online false video injection and offline video streams tampering attacks. The BEVA scheme leverages the electrical network frequency (ENF) embedded in video recordings as an environmental fingerprint for online false frame detection. Blockchain is integrated to enable a decentralized security networking infrastructure, and it empowers an immutable, traceable, and auditable distributed ledger for ENF-based authentication scheme without relying on a third-party trust authority. This secure-by-design solution efficiently provides trust and secure services in IoVT in modern Smart Cities.